Noncorrosive choline chloride composition



Patentecl Aug. 4, 1 953 UNITED NONC ORROSIVE CHOLINE CHLORIDECOMPOSITION Fred W. Schmitz, Terre Haute, Ind., assignor to CommercialSolvents Corporation, Terre Haute, Ind., a corporation of Maryland NoDrawing. Application May 26, 1951, Serial No. 228,529

7 Claims.

This invention relates to choline chloride and more particularly tonon-corrosive choline chloride compositions.

Choline is a vitamin of the B-complex series and it is an importantfactor in nutrition, being indispensable in the performance of many bodyfunctions. The material is used commercially by feed manufacturers as asupplement in feeds for farm animals especially poultry and swine. It isgenerally marketed to such manufacturers in the form of its more stablesalt, choline chloride. Pure crystalline choline chloride is veryhygroscopic and diflicult to handle and distribute uniiormly through afeed mix so the material is preferably marketed in aqueous solution.However, to market choline chloride in this form brings on a verydifficult corrosion problem, choline chloride being corrosive to steel.Thus shipment must be made in plastic lined drums and the material mustbe stored in glass lined tanks or excessive corrosion of the containerstakes place and the choline chloride solution becomes discolored due tothe formation of iron precipitates.

The object of the present invention is to provide an aqueous solution ofcholine chloride which is non-corrosive to steel.

I have now discovered a choline chloride composition which isnon-corrosive to steel, thus making it feasible to ship and storeaqueous choline chloride solutions in ordinary tank cars and in ordinarysteel tanks.

My invention consists of a non-corrosive choline chloride compositionwhich comprises aqueous choline chloride containing a compound selectedfrom the group consisting of alkali metal hexametaphosphates,tetraalkali metal pyrophosphates, alkali metal phytates and alkali metaltripolyphosphates and a compound selected from the group consisting oftartaric acid and citric acid, the pH of the composition being adjustedwithin limits described below.

Due to the fact that when tartaric or citric acids are used in aqueouscholine chloride solutions without the phosphate the overall corrosionrate is actually accelerated, it is entirely unexpected that my newcomposition would prevent corrosion of metal by choline chloride forextended periods of time. Also when the phosphate compounds are usedalone, local type corrosion, commonly called pitting, is accelerated.However, my new composition prevents both types of corrosion and, inaddition, the material of my invention has excellent sequesteringproperties which can be defined as the ability to keep iron in solutionin concentrations whichwould otherwise precipitate as the hydroxide oroxide. This is an important property due to the factthat a slight amountof iron is continuously going into solution (corrosion) in the cholinechloride composition, and if the material did not have a sequesteringeffect the iron would soon become visible through the appearance of agreen turbidity brought about by precipitation of hydrated ironhydroxides which green turbidity would change to a red discoloration asoxidation took place and iron oxides were formed.

The material of my invention is prepared by dissolving in an aqueoussolution of choline chloride, a minor portion of a compound selectedfrom the group consisting of alkali metal hexametaphosphates,tetraalkali metal pyrophosphates, alkali metal phytates (inositolhexaphosphate) and alkali metal tripolyphosphates, then adding to thesolution a small portion of a compound selected from the groupconsisting of tartaric acid and citric acid and finally regulating thepH of the solution by adding an alkali metal hydroxide.

As has been indicated above my invention applies to aqueous solutions ofcholine chloride and especially to commercial preparations of aqueouscholine chloride which are generally of a concentration of about 70%. Myinvention is applicable however, in aqueous solutions of cholinechloride having a concentration as low as approximately 50% but inconcentrations below about 50% there is a sharp drop in theeffectiveness of the corrosion inhibitors which I employ.

The amount of phosphate which I employ in preparing the composition ofmy invention is necessarily very low due to the extremely low solubilityof the phosphates in aqueous choline chloride (less than 0.1 g.phosphate per kg. of aqueous choline chloride at room temperature).Consequently the amount to be used can best be defined as the amountnecessary to form a choline chloride solution which is non-corrosive. Incarrying out my invention, I prefer to use a saturated solution of thephosphate in aqueous choline chloride.

As has been mentioned above, the use of phosphate alone in aqueouscholine chloride solutions is unsatisfactory due to the tendency of thephosphate to cause local type corrosion or pitting. However, for shortperiods of storage the amount of pittin which occurs is negligible andthere is no noticeable effect on the color of the aqueous cholinechloride solution. Therefore, when the aqueous choline chloride solutionis to be used within a period of less than about 20 days after it hasbeen put in steel drums or stored in steel tanks, then the phosphatecorrosion inhibitors are suiiicient in themselves to preserve theaqueous choline chloride solution color-free and the storage containerssubstantially uncorroded.

' The amount of tartaric acid or citric acid to be used for morecomplete protection over extended periods of time is dependent onseveral factors. It has been pointed out above that besides overallcorrosion,. the color of the choline chloride solution must beconsidered as well because while my invention lowers the corrosionrateconsiderably, still some does take place and the iron thus going intosolution must be kept colorless. In the beginning as increasing amountsof acid are added, the overall rate of corrosion is decreased and thelength of time the material stays colorless is increased. However, inthe case of tetraalkali metal pyrophosphates this condition is soondissipated and while increasingamounts of the acid above desirablelimits tend to increase the length of time the material remainscolorless, such increases in tartaric or citric acid content increasethe overall rate of corrosion. For example, as the amount of tartaricacid in the 70% aqueous choline chloride increases 0.01 g. per kg. to0.1 g. per kg. the length of time the material remains color free whenstored in a steel drum increases from to days and the corrosion ratedecreases proportionately. However, as the amount of acid then increasesto 0.5 g. per kg. of aqueous choline chloride the corrosion rateincreases considerably while the length of time the material remainscolor free increases to over 140 days.

This inconsistency is not present when alkali metal hexametaphosphates,alkali metal phytates or alkali metal tripolyphosphates are used, andthus after a certain concentration of acid has been obtained furtheraddition is detrimental to both the overall rate of corrosion and to thelength of time the material remains color free. Considering thesefactors the range of amounts of acid which is operable in my inventionis from 0.01 g. per kg. of choline chloride solution to 1.0 g. per kg.of choline chloride solution. For all of the phosphates included herein,I prefer to use 0.1 g. of acid per kg. of choline chloride solution.

The pH of the final solution is an important consideration of myinvention and the operable range can be defined as being between 7.0 and8.5. Care must be exercised in keeping the pH from the acid side sincethis increases the corrosion rate considerably. I prefer to adjust thepH of my new composition to 8.0 with an alkali metal hydroxide. The pHcannot be adjusted until after the addition of the phosphate and acidbecause of the appearance of a black precipitate if it is adjustedbefore these materials are added.

It is apparent from the description given above that alternate methodsof carrying out my invention are available. For example when tartaric orcitric acid is added and the pH adjusted with an alkali metal hydroxide,the fact that alkali metal tartrate or citrate will be formed is easilyperceived. Thus the possibility of adding the tartrate or citrate saltsas such is suggested and such a procedure is intended to be part of theinvention described herein, this procedure being equivalent to thatspecifically described. In the event such an alternative procedure isused, it should be noted that due to the fact that alkali metaltartrates and citrates are very basic salts, it is desirable to use acidtartaric or citric salts or else the pH of the final composition islikely to be above 8.5. The amount of acid tartrate or citrate which canbe satisfactorily used is within the range of about 0.01 gm. to 1.2 gms.of the acid salt per kg. of aqueous choline chloride.

I A procedure wherein the phosphate is dissolved in the acid and theresulting solution subsequent- 1y added to the aqueous. choline chlorideis also an alternative. to. the specific procedure described herein.With such a procedure, the pH of the final composition must still beadjusted within the limits set forth above.

The following examples are offered to illustrate my invention.Accelerated tests were con ducted wherein a steel strip was suspended ina glass receptacle containing my new choline chloride composition. Theratio of the metal surface of the steel strip to the volume of liquidpresent was. much greater in these tests than the ratio obtained in anordinary 55 gallon drum filled with aqueous choline chloride or in astorage tank containing choline chloride. For this reason corrosiontests carried out over a period of 6 days under the conditionsenumerated below are estimated to be equivalent to corrosion tests indrums which last approximately 60 days and in tanks for much greaterperiods.

EXAMPLE I A six day co rosion test was carried out wherein a carbonsteel strip, 3% inches x 1% inches x inch, was suspended in a Pyrexbeaker containing approximately ml. of a 70% aqueous choline chloridesolution, the aqueous choline chloride being saturated with sodiumhexainetaphosphate and containing the amounts of tartaric acid indicatedin the table. The pH was adjusted to 8.0 with sodium hydroxide. Thecorrosion rate is reported as the per cent of the corrosion rateobtained when a imilar experiment using untreated aqueous cholinechloride was carried out:

Table I C T t d lk f Corrosion lone. ar aric aci ,g. g.o rate, per- 7cholinev chloride cent of Remarks blank 33. 7 no discoloration. 27.3 DO.37.9 DO.

EXAIVIPLE II The tests reported in the following table were conducted inthe same manner as that reported in Example I except that citric acidwas used instead of tartaric acid. The phosphate used is shown in thetable and the amount used was that required to form a saturated solutionin 70% aqueous choline chloride.

The following table shows results obtained when a test similar to thatshown in Example I was carried out using sodium tripolyphosphate as theinhibitor. A saturated solution of sodium trlpolyphosphate in 70% aqueoucholine chloride was used.

Table III C d /k Ootrrosion one. tartaric aci g. g. ra e, per

choline chloride cent of Remm ks blank 30. 3 No discoloration. 28.6 Do.41. 3 Do.

EXAMPLE Iv A choline chloride composition comprising a 70% aqueouscholine chloride solution saturated with tetrasodium pyrophosphate, 0.5g. tartaric acid per kg. of choline chloride solution, the pH of thecomposition being adjusted to 8.0 with sodium hydroxide was stored in a55 gallon steel drum and checked daily for the appearance ofdiscoloration. After 140 days the material was still clear.

EXAMPLE V A choline chloride composition comprising a 70% aqueouscholine chloride solution saturated with sodium hexametaphosphate, 0.01g. tartaric acid per kg. of choline chloride solution, the pH of thecomposition being adjusted to 8.0 with sodium hydroxide was stored in a55 gallon steel drum and checked daily for the appearance ofdiscoloration. After 40 days, the inhibitor broke down as indicated bythe appearance of a green turbidity.

EXAMPLE VI A choline chloride composition comprising a 50% aqueouscholine chloride solution contain ing the indicated amounts oftetrasodium pyrophosphate, 0.5 g. tartaric acid per kg. of cholinechloride solution, the pl-I of the solution being adjusted to 8.0 wasubjected to a six day corro- Six day corrosion tests were carried outwherein carbon steel strips, 3% inches x 1 inches x inch, were suspendedin Pyrex beakers containing approximately 100 ml. of a 70% aqueouscholine chloride solution, the aqueous choline chloride being saturatedwith the phosphates indicated in Table V. The pH was adjusted to 8.0with sodium hydroxide. The corrosion rate was measured as in Example Iand the results are shown in Table V.

Table V Corrosion Phosphate ggi gf Remarks blank Sodium Hexametaphos-40.0 Slight local attack.

hate. Tgtrasodium Pyrophos- 30. 5 Pitted. Slight gelatinous prephate.cipitatc on strip.

This application is a continuation-in-part of my application Serial No.173,683 filed July 13, 1950 now United States Patent 2,576,644.

It is to be understood that the scope of my invention is not to belimited by the amounts and materials indicated in the foregoingexamples. Variations in procedure, materials, and proportions which areobvious to anyone skilled in the art are to be considered as within thescope of the invention as it is described in this specification and theattached claims.

Now having disclosed my invention what I claim is:

1. A non-corrosive choline chloride composition consisting of aqueouscholine chloride solution of a concentration of at least 50% cholinechloride, and an inhibitor selected from the group consisting oftetraalkali metal pyrophosphates, alkali metal phytates, alkali metalhexametaphosphates, and alkali metal tripolyphosphates, the pH of saidcomposition being adjusted to between 7.0 and 8.5.

2. A non-corrosive choline chloride composition consisting of aqueouscholine chloride solution of a concentration of at least 50% cholinechloride, and an inhibitor selected from the group consisting oftetraalkali metal pyrophosphates, alkali metal phytates, alkali metalhexametaphosphates, and alkali metal tripolyphosphates, the pH of saidcomposition being adjusted to from 7.0 to 8.5 with an alkali metalhydroxide.

3. A non-corrosive choline chloride composition consisting of aqueouscholine chloride solution of a concentration of at least 50% cholinechloride, saturated with a compound selected from the group consistingof tetraalkali metal pyrophosphates, alkali metal hexametaphosphates,alkali metal tripolyphosphates, and alkali metal phytates, the pH ofsaid composition being adjusted to from 7.0 to 8.5.

4. A non-corrosive choline chloride composition consisting of aqueouscholine chloride solution of a concentration of at least 50% cholinechloride, saturated with a compound selected from the group consistingof tetraalkali metal pyrophosphates, alkali metal hexametaphosphates,alkali metal tripolyphosphates, and alkali metal phytates, the DH ofsaid composition being adjusted to 8.0.

5. A non-corrosive choline chloride composition consisting of aqueouscholine chloride solution of a concentration of at least about 50%choline chloride, saturated with tetrasodium pyrophosphate, the pH ofsaid composition being adjusted to 8.0.

6. A non-corrosive choline chloride composition consisting of aqueouscholine chloride solution of a concentration of at least about 50%choline chloride, saturated with sodium hexametaphosphgte, the pH ofsaid composition being adjusted to .0.

7. A non-corrosive choline chloride composition consisting of aqueouscholine chloride solution of a concentration of at least about 50%choline chloride, saturated with sodium tripolyphosphate, the pH of saidcomposition being adjusted to 8.0.

FRED W. SCHIVHTZ.

References Cited in the file of this patent UNITED STATES PATENTS Number

1. NON-CORROSIVE CHOLINE CHLORIDE COMPOSITION CONSISTING OF AQUEOUSCHOLINE CHLORIDE SOLUTION OF A CONCENTRATION OF AT LEAST 50% CHOLINECHLORIDE, AND AN INHIBITOR SELECTED FROM THE GROUP CONSISTING OFTETRAALKALI METAL PYROPHOSPHATES, ALKALI METAL PHYTATES, ALKALI METALHEXAMETAPHOSPHATES, AND ALKALI METAL TRIPOLYPHOSPHATES THE PH OF SAIDCOMPOSITION BEING ADJUSTED TO BE TWEEN 7.0 AND 8.5.